In the drilling arts there are known a wide variety of resilient seals which are used to seal about the perimeter of a drill string for various purposes. Such seal assemblies are known by various designations depending upon their intended function, including stripper rubbers, wiper rubbers, packers and blow-out preventers.
The prior art is replete with examples of such sealing apparatus. For example, U.S. Pat. No. 4,531,591 discloses a rotary spindle assembly which includes a resiliently flexible packer. U.S. Pat. No. 4,345,769 discloses a stripper packer which is attached by screw threads to the lower end of a rotary tubular member so as to form a seal between the stripper packer and the tubular member. U.S. Pat. No. 4,486,025 discloses another such seal structure wherein axially extending retention bolts retain a resilient seal member in compression between axially opposed ring elements.
U.S. Pat. No. 3,400,938 discloses a drilling head assembly with a generally conical rubber seal having reinforcements in the form of elongated biasing springs. This patent additionally discloses a clamp or retention ring apparatus formed generally as semi-circular clamp elements which are pivotally connected together adjacent one end and are adapted to accommodate a retention bolt or similar retainer adjacent the opposed ends of the semi-circular ring elements. U.S. Pat. No. 3,965,987 discloses a circumferential clamp ring which employs a wedging action to draw two rigid members axially together, one of which members is a portion of an assembly carrying coaxially arranged rubber seals.
Some of the above characterized structural features are also disclosed in U.S. Pat. Nos. 4,208,056, 3,724,862, 4,658,894, 4,363,357, 4,361,185, 4,441,551 and 4,423,776.
The operations necessary to install such seal assemblies about a drill string in properly sealed engagement with both the drill string and the carrier apparatus have significantly increased the non-productive time element in drilling operations and thus the expense of drilling. For example, stripper rubber change-out has commonly required that a drill string joint be broken apart before the stripper rubber could be removed and replaced. Therefore, the art has continually sought improvements in seal structures such as those characterized above to reduce the difficulty and time consumption involved in their utilization.